1. Field of the Invention
The present invention relates to a multilayer ceramic capacitor and a method for producing a multilayer ceramic capacitor.
2. Description of the Related Art
A multilayer ceramic capacitor includes a sintered ceramic body obtained through the firing of alternately stacked dielectric ceramic and inner electrode layers and outer electrodes formed on both end surfaces of the sintered ceramic body.
With their high capacitance in a small size resulting from such a structure, multilayer ceramic capacitors have become widely used in many applications in the wake of the recent increase in the demand for mobile gear and other portable devices.
Smaller and higher-capacitance multilayer ceramic capacitors are in demand. To meet this demand, researchers are trying to reduce the thickness of dielectric ceramic layers in a multilayer ceramic capacitor. Thinning the dielectric ceramic layers, however, leads to making the field strength per layer relatively high. Dielectric ceramic layers are therefore required to be of higher reliability under voltage, in particular, service life characteristics in high-temperature loading tests.
A known dielectric ceramic layer for multilayer ceramic capacitors contains barium titanate as a major ingredient and some other minor ingredients.
For example, International Publication No. 2009/001597 describes a dielectric ceramic including barium-titanate-based crystal grains and a grain boundary layer existing between the crystal grains. Besides barium titanate, the ceramic contains magnesium, yttrium, manganese, and lutetium.
In International Publication No. 2009/001597, a mixed powder compounded of BaCO3, TiO2, MgO, Y2O3, and manganese carbonate powders is fired into a calcined powder. This calcined powder is mixed with a predetermined amount of Lu2O3 powder, and the resulting mixture is fired. In this way, a desired dielectric ceramic is produced.